Finned envelope heat exchanger



Dec. 21, 1965 R. N. WALLACE 3,224,502

FINNED ENVELOPE HEAT EXCHANGER Filed May 29, 1965 I5 Sheets-Sheet lEUDOLF M W/ILLHC? 7- /Ma/ HTTUE/VV Dec. 21, 1965 R. N. WALLACE 3,224,502

FINNED ENVELOPE HEAT EXCHANGER Filed May 29, 1963 3 Sheets-Sheet 2H77'0E/VEY Dec. 21, 1965 Filed May 29, 1963 R. N. WALLACE FINNEDENVELOPE HEAT EXCHANGER 3 Sheets-Sheet 5 ilited States Patent Office3,224,502 Patented Dec. 21, 1965 3,224,502 FINNED ENVELOPE HEATEXCHAN'GER Rudolf N. Wallace, Glastonbury, Conn, assignor to UnitedAircraft Corporation, East Hartford, Conn., a corporation of DelawareFiled May 29, 1963, Ser. No. 285,547 12 Claims. (Cl. 165-82) Thisinvention relates to heat exchangers and particularly to radiators fortransferring heat from one fluid stream to another.

A most difiicult problem in heat exchange is the transfer of heat from aliquid to a gas. One of the most emcient radiator configurations fortransferring heat from a liquid to a gas is the so-called finned-platetype which has a plurality of hollow envelopes, each of which contains arelatively thin layer of one fluid stream confined between closelyspaced plates of the envelope. The spaced plates are finned on theirexterior surfaces to provide extended surface area in the other fluidstream. However, heat exchangers of the finnedplate type have not beensatisfactory under severe operating conditions, such as for liquid metalradiators. I believe their shortcomings have been due to previously usedmethods of interconnecting passages and of providing mechanicalrestraint against pressure and vibration, requiring matrices which weresolidly welded or brazed together. Because of their complexity, thesecores have been very diflicult to make completely leak-free in initialassembly and, when loaded pressurewise and thermally, they have not beensufficiently flexible to absorb, without failure, the strains which areproduced by thermal and pressure gradients throughout the core matrixand headers.

It is therefore an object of this invention to provide a radiator havinga plurality of finned-plate heat transfer elements which is easy tomanufacture and which permits relative motion between elements so as torelieve the structure of the destructive stresses which result whenthermal strains and pressure deflections are rigidly restrained.

Specifically, the radiator of this invention provides a number ofU-shaped finned-plate elements, identical except for header details,each of which is supported independently by means of inlet and outletconnections to circular manifolds. The elements are self-supporting withrespect to collapsing pressures and are supported against burstingpressures by adjacent elements. Each element is free to expandlongitudinally and transversely as required by thermal expansion andpressure strain. Only one manifold is fixed in the axial direction. Theother is free to position itself according to differences in the lengthof the hot and cold legs of the U-shaped finned elements.

It is a further object of this invention to provide an improved radiatorof the type above outlined.

A further object of the invention is generally to improve radiators.

These and other objects and advantages of the invention will be pointedout in connection with the detailed description of one illustrativeembodiment thereof shown in the accompanying drawings in which a liquidmetal to air radiator is shown by way of example. In these drawings:

FIG. 1 is a side elevation of the radiator embodying the presentinvention shown between the compressor and turbine sections of a gasturbine engine, part of the engine casing and radiator being broken awayto facilitate illustration.

FIG. 2 is an enlarged sectional view on line 22 of FIG. 1.

FIG. 3 is a section on line 33 of FIG. 1 on a larger scale.

FIG. 4 is a section on line 44 of FIG. 1 on a very much larger scaleshowing the finned envelopes in section and illustrating their positionrelative to the tube openings in the headers.

FIG. 5 is an exploded perspective view illustrating one of the U-shapedfinned-envelope elements, the major part of one leg of the U, which isduplicative, being broken away to facilitate illustration.

FIGS. 6, 7, and 8 are sectional views taken on lines 66, 7-7, and 8-8respectively, of FIG. 4 illustrating the three types of headers used forconnecting the envelopes of the outlet manifold.

FIG. 9 is a detailed sectional view through one of the envelopes; andFIGS. 10 and 11 are detailed views showing one of the supports for theoutlet manifold.

In FIG. 1 there is shown the intermediate section 12 of a gas turbineengine between the compressor section 14 and the turbine section 16 ofthe engine. Section 12 includes the usual inner cylindrical casingmember 18 through which the engine shaft extends and the outer casingmember 20 which forms, with member 18, an axial passage 22 which istorus-shaped in cross-section. Passage 22 usually contains a circulararrangement of axially directed burner cans. Herein this passage is0ccupied by the radiator, generally indicated at 24, with which thisinvention is concerned.

The engine casing includes transition sections 26 and 28 between thecompressor and passage 22 and between passage 22 and the turbine inlet.Transition section 26 receives the compressor discharge from annularpassage 30 and directs it into passage 22, divergent annular walls 32and 34 being connected between the walls of compressor discharge passage30 and the cylindrical casing walls 18 and 20, respectively. On thedownstream side of the radiator, convergent annular walls 36 and 38connect cylindrical casing walls 18 and 20, respectively, with tieanular turbine inlet passage 40.

Radiator 24 includes an inner annular manifold 42 and an outer annularmanifold 44. Herein, 42 is the outlet manifold and 44 is the inletmanifold for the liquid metal. Inlet manifold 44 is supported on outercasing 20 by four supporting devices 46, equally spaced about itsperiphery. One of these devices is shown in FIG. 1 and in greatestdetail in FIGS. 10 and 11. Each of these devices includes a shoe 46ahaving an arcuate outer surface which conforms to the inner surface ofouter casing member 24) and is welded thereto. The shoe has two parallelinwardly directed flanges 46b spaced to form a radial slot 460 whichextends transverse to the longitudinal axis of the engine casing toreceive a web 46d welded to manifold 44.

The liquid passages of the radiator consist of a plurality of like,generally radially disposed finned-plate elements in the form ofU-tubes, the ends of which are connected to manifolds 42 and 44. Eachtube includes parallel elongated legs 52 and 54 flattened and curvednormal to their length. Legs 52 and 54- are connected together at theirdownstream ends by headers 56 and 58 respectively and header connectors60 (FIG. 5). At their upstream ends the legs 52 are connected bysuccessive groups of headers 64, 64a and 64b and header tubes 65 toinner manifold 42. It will be noted that inner and outer manifolds 42and 44 have annular flattened faces adjacent the radiator. Face 70 ofmanifold 42 is provided with three annular rows of staggered tubeopenings 72, 74 and 76 arranged to receive header tubes 65 of headers64, 64a and 64b, respectively (FIGS. 6, 7 and 8) of successive groups oflegs 52 about its periphery. Outer manifold 44, having a longerperipheral dimension, is similarly provided with two annular rows ofstaggered openings 78 and 30 arranged in its annular face 70 to receivein a like manner staggered annular rows of header tubes 82 leading toheaders 81 of alternate legs 54. One of these tubes is shown in FIG. 1.

Inner manifold 42 is provided with an outlet pipe 84 and outer manifold4-4 is provided with a similar inlet pipe 86 for the liquid which, inthis radiator, is liquid metal, these inlet and outlet pipes beingconnected, as shown herein, to the manifolds 42 and 44 at the bottom ofthe engine.

It will be noted from FIG. 1 that the liquid containing elements of theradiator and their connected manifolds 42 and 44 do not completely fillthe torus-shaped axial passage 22 between casing members 18 and 20, aninner annular passage 88 being provided between casing member 18 and theradiator elements and an outer annular passage 90 being provided betweencasing 20 and the radiator elements. An annular seal 92 (FIG. 4) closesoff passage 96 at the upstream end of the radiator, this seal comprisingan annular flange 92a carried by the radiator which is received in aslot formed by parallel flanges 92b on a continuous annular shoe whichhas a sliding connection with casing member 20.

A similar annular seal 94 having an annular shoe slidable on casingmember 18 is carried by the radiator at its downstream end which closesoff the annular passage 88. The seals 92 and 94 are very similar inconstruction to the support devices 46 for manifold 44 shown in detailin FIG. 11 except that the annular shoe is not welded to the casingmember. As a result, air discharged from the compressor entering axialpassage 22 is forced inwar-dly into passage 88 from which it is forcedto flow substantially radially through the spaces between the plateelements of the U-tubes into passage 90 and into turbine inlet passage40.

To insure this generally radial flow and to increase the surface area ofthe plate-like elements of the tubes, corrugated panels 96 are brazed orwelded to both outer surfaces of legs 52 and 54 of the tubes, as shownin FIGS. 2, 3 and 4. The corrugations are rectangular in cross sectionand the flat outer faces 98 of each panel 96 on an envelope abut thelike flat face of the panel on the opposite side of the next adjacenttube.

Ribs, or air baflles, 100 are also brazed to each platelike element ofthe tubes along opposite sides thereof at -the upstream and downstreamends of the radiator to confine the cooling air to the finned area ofthe tubes. These completely enclose the ends of the plate-like envelopesas shown in FIG. 9 and abut the ribs of adjacent envelopes to form acomplete closure at the upstream and downstream ends of the radiatormatrix and to further support the envelopes against compression forces.The adjacent air baffles 100 of legs 52 and 54 abut along 'line 102(FIG. 4), further supporting the radiator elements. The curvature of theflattened tubes and their corrugated panels 96 and ribs 100 is ofinvolute form so that each element is of constant width and, whencombined with the other elements, they completely fill the annulartorusshaped space alloted to the radiator core.

Collapsing loads are carried by the fin panels, acting as transversebeams, to a number of bearing strips 104 (FIG. 5) running lengthwise ofthe radiator in the liquid passage of the flattened tubes. These bearingstrips, which are H-shaped in cross section, are either loosely locatedby stops or are attached to one wall only by brazing so they cannotcarry any tension loads between the sides of the tubes. Besides takingcompression loads these strips also serve to distribute the liquid flowevenly over the entire area of the envelopes.

In the operation of the radiator, air discharged from the compressorsection 14 flows through the transition section 26 from the annularcompressor discharge passage 30 to the upstream end of passage 22. Sincethe annular barrier 92 closes off passage 20 between the radiator andcasing 20, and since the air baflles 1&0 on the upstream ends of theradiator envelopes completely close 01f the frontal area of thetorus-shaped radiator, the entering air is obliged to flow inwardly intoannular passage 88 between the inner casing member 13 and the innerperiphery of the radiator. This annular space 8% is also closed off atthe downstream end of the radiator by the annular air seal 94.Consequently the air is obliged to flow from passage 88 between theenvelopes 52 and 54 into the outer annular passage 90. Further, in itspassage through the radiator, the air in passage 88 is distributedevenly over all of the envelopes in the torus-shaped radiator by reasonof the corrugated panels 96. From the annular passage 90 the air heatedby the radiator passes into transition section 28 and from thence intoannular turbine inlet passage 40.

Liquid metal entering the radiator through conduit 86 enters the outerannular manifold 44 from which it is fed into the radiator throughheader tubes 82 which are arranged in staggered relation in two circularrows about the flat face 76 of manifold 44, a tube 82 from the outsiderow supplying the header of one envelope and a tube from the inside rowsupplying the header of the next envelope. The fluid in each of theheaders 81 of the outer legs 54 of the U-shaped finned elements isdistributed evenly over the envelope space by the bearing strips N4which divide the envelope into a plurality of axial flow passagesleading to the header 58 at the downstream end of leg 54. The liquidmetal then flows through the header connector 60 into header 56 of theinner leg 52 of the U-tube. Here again the liquid metal is distributedover the surface of the envelope by bearing strips 104 as it flowsaxially forwardly through the envelope into headers 64, 64a, and 64bwhich are shown in FIGS. 6, 7 and 8. These headers are connectedserially around the outlet manifold 42 into tube openings 72, 74 and 76in the annular flattened face 70 of manifold 42. The arrangement ofthese tube openings is shown in FIG. 4 from which it will be evidentthat the finned-plate element of the first tube, beginning at the leftof the figure, is connected to one of the tube openings 72. The tube 65of the next element is connected to a tube opening 76 and the element 65of the next tube is conneeted to atube opening 74 and so on about themanifold 42. In this way the tubes 65 can be of suflicient size to carrythe flow from the envelopes while preserving the close spacing of thelatter. From manifold 42 the liquid metal is discharged through outletconduit 84. It will be noted that the inlet and outlet conduits 86 and84 are shown herein only at the bottom of the radiator. However, ifdesired, such conduits may be provided at other points about theperiphery of the manifolds.

From the above description it will be evident that a radiator has beenprovided herein consisting of a number of finned plate elements,identical except for header details, each of which is supportedindependently through inlet and outlet connections to circularmanifolds. It Will also be evident that the elements are self-supportingwith respect to collapsing pressures and that each is supported againstbursting pressures by adjacent elements. Each element is independentlyfree to expand longitudinally and transversely as required by thermalexpansion and by pressure strain. Only one manifold, herein manifold 44,is fixed in the axial direction. The other is free to position itselfaccording to differences in the length of the hot leg 54 and the coldleg 52 of the U-tube. Both manifold 42 and manifold 44 are allowedfreedom of radial movement in all directions.

It will be understood that the same scheme can be used to producerectangular radiators by assembling elements which are fiat rather thanbeing formed to an involute curve. In such an arrangement the radiatorair case must bear against the outer corrugations of the two endelements in order to provide support against bursting pressures.

While only one embodiment of the invention has been shown and describedherein, which is particularly adapted to the air flow pattern of anaxial flow gas turbine engine, it will be evident that variations may bemade in the construction and arrangement of the parts for otheradaptations without departing from the scope of the following claims.

I claim:

1. In a radiator for transferring heat from one fluid stream to another,elongated concentric cylindrical casing members defining a toroidalshaped chamber therebetween, a radiator matrix comprising a plurality ofelongated U-shaped tubular elements the parallel legs of each of whichare flattened and curved normal to their length to form hollow envelopeswhich lie in the same curved planes, said elements being arrangedside-by-side in a circle about said toroidal chamber with their flatside surfaces in juxtaposition, inner and outer annular manifolds, oneadjacent the inner casing member, the other adjacent the outer casingmember, conduit means for connecting the inner legs of said U-shapedelements at their free ends to said inner manifold, conduit means forconnecting the outer legs of said elements at their free ends to saidouter manifold, means for fixedly supporting one of said manifoldsagainst axial movement on the adjacent casing member While permittinglimited radial movement relative to said casing member, and means forsupporting the other manifold for free axial and lateral movementrelative to said casing members.

2. The radiator of claim 1 having corrugated metal panels secured to theopposite sides of the envelopes with the corrugations running transverseto the longitudinal axes of said envelopes, said envelopes being closelyspaced with the tops of the corrugations on adjacent envelopes inabutting relation, whereby said envelopes support one another againstbursting pressures.

3. The radiator of claim 1 having means within the envelopes forresisting collapsing pressures, said means comprising bearing stripsextending longitudinally of said envelopes in spaced relation over thearea of said envelopes.

4. The radiator of claim 2 in which an annular space is provided betweenthe inner casing member and the matrix and an annular space is providedbetween the outer casing member and the matrix, means for directing theincoming cold fluid into said inner space, and means for discharging theheated fluid from said outer space.

5. The radiator of claim 4 in which curved fluid baffles are secured tothe opposite curved surfaces of each envelope at its axial extremitieswhich engage the bafiies of adjacent envelopes and confine the fluidflow between said inner and outer spaces to the passages between saidcorrugations, the curvature of said envelopes being involute so that theenvelopes with the baffles thereon present closed areas at the ends ofthe matrix.

6. The radiator of claim 5 in which the fluid bafiies are commensuratein height with the corrugations of said panels and engage the bafiies ofadjacent envelopes to support the envelopes against bursting pressures.

7. In a liquid-metal-to-air radiator, an axially elongated casing havingspaced cylindrical inner and outer casing members defining a toroidalchamber for the air flow, a plurality of U-shaped tubes extendingaxially from the upstream end to the downstream end of said chamber,said tubes being compressed to form hollow plate-like elements in theplane of the tube which are arranged in said chamber with the plane ofthe tube generally radially disposed in said chamber with the open endsof the tubes at the upstream end of said chamber, means for directing astream of air into the upstream end of said chamber, means fordischarging said air from the downstream end of said chamber, an innercircular manifold in the upstream end of said chamber adjacent saidinner casing member, an outer circular manifold in the upstream end ofsaid chamber adjacent said outer casing member, one of said manifoldsbeing fixed to the adjacent casing member and the other being free tomove relative to said casing, a header closing each of the free ends ofeach tube, a conduit connecting said inner manifold with the headers atthe inner ends of said tubes, and a conduit connecting said outermanifold with the headers at the outer ends of said tubes.

8. In a liquid-metal-to-air radiator, an axially elongated casing havingspaced cylindrical inner and outer casing members defining a toroidalchamber, a radiator matrix comprising a plurality of U-tubes forming thefluid passages of the radiator having each leg flattened and curvednormal to its length, the legs at the closed end of the U terminating inheaders, means for connecting said headers together, headers at the openends of said U tubes, an inner circular manifold in said chamberadjacent the inner open ends of said U tubes, said manifold having anannular tube sheet confronting the headers of said inner open ends ofsaid U tubes, header tubes connecting said inner headers with said tubesheet, an outer circular manifold in said chamber adjacent the outeropen ends of said U tubes, said outer manifold having an annular tubesheet confronting the headers of said outer open ends of said U tubes,header tubes connecting said outer headers with said outer manifold,means for rigidly connecting one of said circular manifolds to acylindrical casing member, fluid connections to said inner and outermanifolds, curved corrugated panels carried by said curved legs of saidU tubes, said panels of each tube abutting panels of adjacent tubes,means for directing a stream of air into said chamber at its upstreamend, air baflies for directing said air within the toroidal matrix ofsaid radiator and into the spaces formed by the corrugations of saidpanels, and means for discharging said air at the downstream end of saidchamber.

9. In a two-pass hot-liquid-to-air radiator, the combination of anelongated toroidal casing having a transition section at its upstreamend receiving the discharge from a compressor and a transition sectionat its downstream end discharging into a gas turibne, outer and innerspaced concentric manifolds at the upstream end of said casing, saidmanifolds having liquid outlet and inlet connections and only one ofsaid manifolds being fixedly supported by said casing at said upstreamend against axial movement, inner and outer banks of hollow flatenvelopes arranged in side-by-side relation about said toroidal casingand extending lengthwise of said casing, said envelopes in said innerand outer banks abutting each other and being closed at their abuttingends, said inner bank of envelopes having fluid connections with saidinner manifold and said outer bank having fluid connections with saidouter manifold, means for establishing fluid connections between saidenvelopes of said banks at their downstream ends, means for directingair entering said casing from the compressor into an annular passage insaid casing within said inner bank of envelopes, and extended surfacemeans between adjacent envelopes for directing said air over thesurfaces of said envelopes.

It In a liquid-metal-to-air radiator, a core structure comprising aplurality of elongate U tube elements having each leg flattened andcurved normal to its length to provide hollow plate-like envelopes,headers closing the ends of the envelopes at the closed ends of the tubeelements, header connectors connecting the headers of each element,corrugated panels secured to opposite faces of said envelopes, thecurvature of said envelopes being involute so that when said U shapedelements are arranged in side-by-side abutting relation they form atorus in which the elements provide mutual lateral support for eachother against internal pressures, the spaces between the corrugationsserving as passages for the air through the core and said envelopesserving as the liquid metal passages through the core.

11. In a liquid-to-metal-to-air radiator, a core structure comprising aplurality of elongate-d U tube elements having each leg flattened andcurved normal to its length to provide hollow plate-like envelopes,headers closing the ends of the envelopes, header connectors connectingthe headers at the closed ends of the U tube elements, curved corrugatedpanels secured to the opposite faces of said envelopes, the curvature ofsaid envelopes and their panels being involute so that when saidelements are arranged in side-by-side relation they form a solid torusin which the elements provide mutual lateral support for each otheragainst internal pressures, inner and outer circular manifolds at theunconnected ends of said legs, tubes connecting the header of the innerleg of each element to said inner manifold, tubes connecting the headerof the outer leg of each element to said outer manifold, liquid metalinlet and outlet connections to said manifolds, and means for directinga stream of air to flow through the spaces formed by the corrugations ofsaid abutting panels.

12. A liquid-metal-to-air radiator comprising, a plurality of elongatedU tubes forming the liquid passages for the radiator, said tubes havingeach leg flattened and curved normal to its length, pairs of curved ribsbrazed to opposite sides of each leg at its ends forming air baffles,corrugated curved panels brazed to opposite sides of said legs andextending between said ribs, the curvatures of said legs being involuteso that when arranged in side-byside relation said tubes form acontinuous solid matrix of toroidal shape, inner and outer cylindersforming an elongated torus-shaped chamber for said matrix, inner andouter circular manifolds located at the open ends of said U tubes, tubesconnecting said inner manifold to the headers of corresponding innerlegs of said U tubes, tubes connecting said outer manifold to theheaders of corresponding outer legs of said U tubes, liquid metal inletand outlet connections for said manifolds respectively, means fordirecting a stream of air into the upstream end of said chamber, meansfor discharging said air stream downstream of said chamber through thepassages formed by the corrugations on said panels first across one legof said U tubes then the other, and baflle means in said chamber fordirecting air to flow generally radially across said envelopes means forfixedly supporting one of said manifolds against axial movement on anadjacent cylinder, and means for supporting the other manifold on anadjacent cylinder for freedom of movement both axially and laterally.

References Cited by the Examiner UNITED STATES PATENTS 1,830,375 11/1931Shoop 165164 2,053,780 9/1936 Price et a1. 16581 2,409,801 10/1946 Rueggl26109 2,444,908 7/1948 Bailey et al. l172 X 2,582,134 1/1952 Kimmell etal 81 X 3,033,534 5/1962 Caughill et al. 165-82 FOREIGN PATENTS 501,8493/1939 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

SAMUEL FEINBERG, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,224502 December 21, 1965 Rudolf N. Wallace It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 2, line 56, column 5, line 11, column 6, lines 11, 58 and 74, andcolumn 7, line 19, for "length", each occurrence, read width Signed andsealed this 31st day of January 1967.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents

1. IN A RADIATOR FOR TRANSFERRING HEAT FROM ONE FLUID STREAM TO ANOTHER,ELONGATED CONCENTRIC CYLINDRICAL CASING MEMBERS DEFINING A TOROIDALSHAPED CHAMBER THEREBETWEEN, A RADIATOR MATRIX COMPRISING A PLURALITY OFELONGATED U-SHAPED TUBULAR ELEMENTS THE PARALLEL LEGS OF EACH OF WHICHARE FLATTENED AND CURVED NORMAL TO THEIR LENGTH TO FORM HOLLOW ENVELOPESWHICH LIE IN THE SAME CURVED PLANES, SAID ELEMNETS BEING ARRANGEDSIDE-BY-SIDE IN A CIRCLE ABOUT SAID TOROIDAL CHAMBER WITH THEIR FLATSIDE SURFACES IN JUXTAPOSITION, INNER AND OUTER ANNULAR MANIFOLDS, ONEADJACENT THE INNER CASING MEMBER, THE OTHER ADJACENT THE OUTER CASINGMEMBER, CONDUIT MEANS FOR CONNECTING THE INNER LEGS OF SAID U-SHAPEDELEMENTS AT THEIR FREE ENDS TO SAID INNER MANIFOLD, CONDUIT MEANS FORCONNECTING THE OUTER LEGS OF SAID ELEMENTS AT THEIR FREE